"Great -- head panel meaning the panel that you would take off to change the headlight bulb, etc. ?"
Not sure of the year but it should be the same as mine. Its the panel that covers the "handle bars" where the speedometer is. The screw is right next to the throttle grip.
OK, so now that I took off the whole panel and took the throttle grip apart, now I realize that you meant the screw that's below the panel (like you said) and it was exposed the whole time, haha.
Problem is, I was watching the throttle, and turning the grip, and adjusting that screw from one extreme to the other, and I couldn't ever see any difference. I'd think that unscrewing it all the way would be the best for my problem, because then it's like the casing it travels through is longer and the cable stays the same length, so it's tighter... right?
-Joe